The present invention relates to spur gearing for a drive, particularly the drive of a roller shell.
Spur gearing of this type is known from Federal Republic of Germany Patent No. 33 30 204 which corresponds to U.S. Pat. No. 4,676,117. It is particularly suitable for driving a hollow roller shell which rotates around a stationary inner part, like a beam, from which it is radially spaced. Rollers of this type comprise, for example, sag adjustment rollers or suction rollers which are used in the paper-making industry, for instance in water-removal presses, calenders, or the like. A preferred field of use of the invention is on equidistantly mounted sag adjustment rollers. In these, the bearings of the roller shell, the bearings of the mating roller and the spherical supports of the yoke((a flexure beam or girder which extends through the roller shell) are arranged with at least approximately the same bearing spacing, as described in U.S. Pat. No. 4,414,890 and its reissue, Re. No. 32,856.
FIG. 3 of U.S. Pat. No. 4,414,890 (but not its reissue) also shows spur gearing for the driving of the roller shell. In that case, as in the present invention, the outer gear rim is firmly attached to one end of the roller shell. Upon operation of the roller under load, if the roller shell sags, then the outer gear rim inclines slightly, together with the axial end region of the roller shell, relative to the non-inclinable gear housing. That housing at the same time serves as a support bracket for the entire roller. Upon standstill or roller operation without load, the roller can be lifted by the shifting of the supporting bracket away from the mating roller. In that case, under certain circumstances, the entire roller may assume a slightly oblique orientation. Also, in this case the outer gear rim inclines slightly relative to the support bracket or gear housing. In all cases, the outer gear rim inclines such that it tilts slightly around its center point. For supporting the roller shell, there is within the outer gear rim a first self-aligning bearing having a center point also lying at least approximately in the central plane of the outer gear rim which is perpendicular to the axis of rotation of the roller. The pinion which meshes with the outer gear rim is mounted in a similar manner. In this way, the pinion can follow the inclining of the outer gear rim.
However, this measure alone does not assure that the axes of the two gear wheels will remain at least approximately parallel to each other upon transfer of torque by the gearing. Yet, such a parallel orientation is necessary in order that the meshing gear wheels can always transfer the full torque Thus, in the arrangement of FIG. 3 of U.S. Pat. No. 4,414,890, during the transmission of torque, there is a danger that the pinion will tilt out of its normal position in which the axes and tooth flanks of the two gear wheels are parallel to each other. When the gears become tilted out of position, then the teeth still contact each other, but only in a narrow region in the center of the gears. This presents the danger that the gears will be overloaded.
Measures to eliminate this danger are suggested in U.S. Pat. No. 4,676,117. At merely one axial face side of the outer gear rim and the pinion, there is a single pair of stop collars which travel on each other. Special means assure that these stop collars are held in contact with each other during roller operation. The stop collars are so dimensioned, that is, they are of such radial dimensions, that tilting of the pinion out of its normal position parallel to the outer gear rim is impossible during roller operation. That means which maintains the contact between the stop collars must produce a tilting moment on the pinion. Two possibilities for this are disclosed in U.S. Pat. No. 4,676,117. In one of them, this tilting moment is produced via a spiral toothing of the gear wheels. This has the disadvantage that only one direction of roller rotation can be used. In the second possibility for producing a tilting movement, the tooth coupling shaft is arranged obliquely to the pinion axis. This has the disadvantage that upon reversal of the direction of roller rotation, the direction of the oblique arrangement of the tooth coupling shaft must be changed.